As is well known in the art, in a typical recriprocating high-pressure compressor, lubrication fluid is continually injected into the compressor bearings and the various seals in the compression chamber of the compressor. Typically, the lubricant is injected into the bearings at a pressure in a range of about 25 to 50 psi, and into the seals at a pressure at least as high as the pressure of the gas in the compression chamber which generally is in excess of 1000 psi.
In order to maintain complete lubrication of the bearings and seals under these diverse pressure conditions, it has been the practice to provide a separate bearing oil pump in the compressor which is adapted to pump a continuous flow of oil from the crankcase of the compressor into the bearings, and a second high-pressure pump which is adapted to inject oil into the seals. In general a high-pressure reciprocating pump has been used to inject the oil into the seals since reciprocating pumps have the inherent advantage of pumping the same known quantity of fluid during each operating cycle. Thus, the pumping rate of such pumps can be controlled with considerable accuracy by controlling the frequency at which the pumping cycle is repeated. Accordingly, both electronically and mechanically operated reciprocating pumps have been used for this purpose.
In electronically controlled pumps, a suitable switching circuit is generally used to control the frequency of the pumping cycle, and in the various mechanically controlled pumps, a series of cams, sprockets, and chains are usually coupled to the drive shaft of the compressor to control the pumping cycle. By way of illustration, U.S. Pat. No. 4,028,014 shows a double-acting piston type fluid pump which is cyclically reversed by solenoid valves actuated by electrical switches located at each end of the piston stroke, and U.S. Pat. No. 3,180,527 shows a double-acting pump which is cyclically reversed by a reversing valve actuated by a mechanical camming arrangement connected to a rotating output shaft on a timer.
While electrically controlled pumps have proven satisfactory in many applications, there are a number of cases where the use of electrical power is inappropriate or the power is simply not available. In those applications, is has been the practice to use one of the various mechanical cam and sprocket arrangements to control the pump. However, in many of those applications, the operating environment of the pump and the relative complexity of the cam and sprocket arrangement result in frequent breakdowns and downtime while the pump is being repaired.